Make <style> work for disconnected shadow trees

Fixes #1194.

source

@@ -14114,8 +14114,11 @@ c-end         = "-->"</pre>
    <li><p>If <var>element</var> has an <span>associated CSS style sheet</span>, <span
    data-x="remove a CSS style sheet">remove the CSS style sheet</span> in question.</p></li>
 
-   <li><p>If <var>element</var> is not <span>in a shadow-including document</span>, then abort these
-   steps.</p></li> <!-- http://software.hixie.ch/utilities/js/live-dom-viewer/saved/2740 -->
+   <li><p>If <var>element</var>'s <span>root</span> is neither a <span>shadow root</span> nor a
+   <span>document</span>, then abort these steps.</p></li>
+   <!-- http://software.hixie.ch/utilities/js/live-dom-viewer/saved/2740
+        Also, per https://github.com/w3c/webcomponents/issues/56 stylesheets should work in
+        disconnected shadow trees. -->
 
    <li><p>If the <span>Should element's inline behavior be blocked by Content Security
    Policy?</span> algorithm returns "<code data-x="">Blocked</code>" when executed upon the